Odds of Getting In
Slim, unless you're the son of a player, the son of a coach, the brother of a player, or in Eli Manning's case, all three.
The leap from high school football to college football crushes the dreams of many, many hometown football heroes. Only 3-4% of high school players get the opportunity to play college football, and those players are not necessarily the most talented or athletically gifted. To be recruited by any college (not just one that Lee Corso occasionally visits on Saturday mornings), players need to catch the eye of the coach, and then prove to have the combination of athletic ability, mental toughness, and intelligence (both on the football field and in the classroom—the work ethic that one applies to schoolwork counts, too) to keep the coach’s attention. And even then, if the player's skills don't match up with exactly what the coach is looking for, he's probably going to be part of the 96% who only pick up footballs that say "NERF" on the side.
But college football is just one step on the path to professional football—you still have to play well enough for two to four years of college (and theoretically work on getting a college degree at the same time) to make enough of an impression on at least one NFL team to get drafted. The ways players can make this impression are not restricted to the 10 to 13 games each college team plays every year. Each college can hold a Pro Day, where the eligible players from the college work out for NFL scouts and team representatives. Selected players are also invited to attend the NFL Combine, where they are tested in events including the 40-yard dash (where the time it takes to run 40 yards is recorded), the bench press (where the number of times a player can lift 225 pounds is recorded), and the shuttle run (where the player has to carry two suitcases while running to catch an airport shuttle before it leaves the parking lot).
The exact number of players who are eligible to be drafted every year is not readily available, but with some basic math skills, we should be able to come up with a rough estimate. There are 115 colleges with NCAA Division I football programs, give or take half a dozen in any given year. These colleges can offer up to 85 scholarships per year, but every team has some non-scholarship players, so let's estimate that there are an average of 110 players on a Division I team. A quick check of the rosters shows that each team has between 10 and 20 seniors. So let's say that each team has an average of 15 seniors. That makes for a total of 12,650 players, with 1,725 seniors. But that doesn't count Division II, which has roughly the same number of teams, so double those numbers to 25,300 players and 3,450 seniors. So the first lesson that our foray into math offers is that not every college football player makes it to his senior year, and being offered a scholarship out of high school is no guarantee of eventually entering the NFL draft.
So, including the 50 or so underclassmen who leave college and declare themselves eligible for the NFL draft, that’s a pool of 3,500 players who could be drafted. Now consider the number of players who were drafted by NFL teams in 2011: 254. In other words, only approximately 7% of eligible players get drafted. Those players then have to compete with everyone else on the roster, plus any undrafted college free agents (that is, players who weren't drafted but are still offered the chance to try to make the roster), plus any other veterans or players from other leagues the team might want to check out, just to make it onto the Week 1 roster.
To make a long story short (too late), the odds of going from high school football to college football to the NFL are not good.